Categorical stimuli bias episodic memory: Evidence from behavior, lesion patients, and neuroimaging

Poster Session B - Sunday, April 14, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Hillary Schwarb¹ (hschwarb2@unl.edu), Michael R. Dulas², Melissa C. Duff³, Neal J. Cohen⁴; ¹University of Nebraska-Lincoln, ²Binghamton University, ³Vanderbilt University Medical Center, ⁴University of Illinois at Urbana-Champaign

Categorical stimuli can bias episodic memory in interesting ways. When categories can be used to chunk information, memory improves. Conversely, when remembering multiple category exemplars, intrusion errors are common. To assess category bias and the supporting neural corelates in associative/relational memory, we conducted a series of studies using a spatial reconstruction task where on each trial, stimuli came from two distinct categories. Both hippocampus and ventral prefrontal cortex (vPFC) support relational memory, but their contributions to category-bias effects are unknown. In Experiment 1, we characterized category bias in spatial relational memory demonstrating that when two categories of stimuli are present, healthy young participants make significantly more within-category misplacement errors than between-category misplacement errors, despite 50% more opportunities for between-category errors. These data suggest that memory representations were organized to prioritize keeping distinct categories separate and deprioritize resolution of same-category stimuli. In Experiment 2, individuals with bilateral hippocampal or vPFC lesions completed this task. Individuals with vPFC damage made equal numbers of within- and between-category misplacement errors suggesting that their memory was not biased in the same way as comparison individuals. Individuals with hippocampal damage were globally impaired. In Experiment 3, fMRI was used to assess the neural contributions to this behavior in healthy individuals. During study, activity on two-category vs. single-category trials revealed significant activity in the vPFC further implicating this region’s role in organizing relational memory representations when multiple stimulus categories are present. Together these data support the role of vPFC in organizing relational memory representations.

Topic Area: LONG-TERM MEMORY: Episodic